The present invention relates to saw blades, and more particularly, to saw blades particularly suitable for cutting structural steel, such as angle irons, I-beams, tubing and the like.
Structural band saw blades are used to cut structural steel, such as angle irons, I-beams, tubing and the like. In these applications, the band saw blades are typically run at relatively high speeds on the order of about 300 surface feet per minute, with relatively little, if any, coolant. Typically, the coolant is sprayed in a mist onto the blade at a location about two to three feet in advance of the inlet to the cut. Certain prior art structural band saw blades have tended to allow excessive collection of chip curls in the gullets of the blades which tend to be forced back into the cutting zone and, most importantly, into direct contact with the primary rake face. As a result, there is an increase in both the cutting forces and overall chip contact length with the rake face which, in turn, cause the amount of heat transferred into the blade to increase and adversely effect overall blade life. In some instances, the heat build-up is sufficient to weld chip curls to the cutting edges of the blades and, in turn, fracture the cutting edges when the chip curls are broken away.
Cutting structural steels, as opposed to solid blocks, for example, involves intermittent cutting, and the degree of such intermittent cutting depends upon the shape and/or configuration of the work pieces being cut. Intermittent cutting with prior art structural band saw blades causes substantial chatter and vibration in the blades, and unbalanced loading among the teeth of the blades. This, in turn, leads to higher rates of tooth strippage in comparison to other types of cutting operations.
Accordingly, it is an object of the present invention to overcome one or more of the above-described drawbacks and disadvantages of the prior art.
The present invention is directed to a structural saw blade, such as a band saw blade, comprising a cutting edge defined by a plurality of teeth spaced relative to each other. Each tooth of the saw blade includes a tip, a rake face formed on one side of the tip, and a primary clearance surface formed on the opposite side of the tip relative to the rake face and defining a primary acute relief angle. A secondary clearance surface is formed on the opposite side of the primary clearance surface relative to the tip, and the secondary clearance surface defines a secondary acute relief angle that is less than the primary acute relief angle. In addition, a tertiary clearance surface is formed on the opposite side of the secondary clearance surface relative to the first clearance surface, and defines a tertiary acute relief angle that is greater than the primary and secondary relief angles.
A weld zone of each tooth is formed between the tip and the back edge of the saw blade and extends in the elongated direction of the blade from approximately one side of the tooth to the other. A rake face protrusion is formed on the opposite side of the rake face relative to the tip, and extends over one end of the weld zone. The rake face protrusion projects outwardly relative to a plane defined by the rake face, and the secondary and tertiary clearance surfaces project outwardly on the opposite side of the tooth relative to the rake face protrusion. At least one of the secondary and tertiary clearance surfaces extends over the weld zone on the opposite side of the tooth relative to the rake face protrusion to thereby form an increased tooth thickness at the weld zone.
In accordance with a preferred embodiment of the present invention, the saw blade is a structural band saw blade, the primary acute relief angle is within the range of approximately 20xc2x0 through approximately 35xc2x0 relative to a plane defined by a back edge of the blade, and most preferably is approximately 27xc2x0 relative to the back edge of the blade; the secondary acute relief angle is within the range of approximately 5xc2x0 through approximately 20xc2x0 relative to a plane defined by the back edge of the blade, and most preferably is approximately 15xc2x0 relative to the back edge of the blade; and the tertiary acute relief angle is within the range of approximately 40xc2x0 through approximately 55xc2x0 relative to a plane defined by the back edge of the blade, and most preferably is approximately 46.5xc2x0 relative to the back edge of the blade.
Also in accordance with a preferred embodiment of the present invention, the rake face protrusion defines a surface area of maximum projection relative to a plane of the rake face that is spaced at a depth below a cutting plane of the tip of an unset tooth within the range of approximately 0.030 inch through approximately 0.100 inch, and most preferably within the range of approximately 0.045 inch through approximately 0.075 inch. In addition, the rake face protrusion preferably defines a thickness normal to a plane of the rake face within the range of approximately 0.005 inch through approximately 0.060 inch.
Also in accordance with a preferred embodiment of the present invention, the blade defines extended pitch patterns, preferably at least approximately 9 teeth per pitch pattern, with set patterns within each pitch pattern. In addition, the preferred embodiments of the band saw blades of the present invention preferably define variable level height and set patterns within each pitch pattern.
One advantage of the saw blades of the present invention is that the rake face protrusion, in combination with the locations of the secondary and tertiary clearance surfaces as defined by the respective clearance angles, significantly increase the width or thickness of each tooth at the weld zone in comparison to prior art structural saw blades, and thereby substantially improve the resistance to tooth strippage as encountered with such prior art blades. Yet another advantage of the preferred embodiments of the present invention is that the variable level height and set of the teeth provide a relatively deep and narrow cut for each tooth operating to reduce the torque loads on the teeth in comparison to prior art saw blades, and the extended pitch patterns defining relatively uniform distances between teeth of like set direction further facilitate reducing noise and vibration to thereby enhance blade life in comparison to prior art band saw blades.
Other advantages of the present invention will become readily apparent in view of the following detailed description of preferred embodiments and accompanying drawings.